Egg-shell structured LiCoO2 by Cu2+ substitution to Li+ sites via facile stirring in an aqueous copper(ii) nitrate solution

For practical, high-energy lithium ion batteries, we introduce an egg-shell structured LiCoO₂, enabling a credible performance with a high cut-off potential of 4.4 V, simply prepared by only stirring in 0.5 mM Cu(NO₃)₂ aqueous solution at room temperature without costly heat treatment.